Electronic devices and information processing devices including game devices and home appliances that are available in recent years provide significantly advanced functions. In association with this, the system that allows a user to provide an input through a user interface has become increasingly complicated. Various improvements have been made to user interface so that a use can provide an input easily using such a complicated input system. For example, attempts have been made to use different approaches to assignment of functions to controller buttons or to use a touch panel. Also proposed are technologies of performing processes adapted to change in the orientation of the user's face by analyzing an image acquired by using a device designed to capture an image of the user as an interface (see, for example, patent document No. 1).
By using an image capturing device as a user interface, face recognition technology can generally be used to detect, for example, the state of the user's face. For example, facial portions may be detected by computing a matching score between a reference image prepared in advance and an image of the detected facial region or by extracting characteristic points, so that temporal change in the state of the user's face may be acquired.    [patent document No. 1] JP 2008-112360